/*
 * Copyright (C) 2012 Roman Yakovenko <b179a9@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is furnished to do
 * so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package com.b17.crypto.provider;

import com.b17.crypto.core.Utils;

public class RC4 implements Cipher {
    private byte[] sbox = new byte[256];

    public static final int KEY_SIZE = 32;

    int x, y;

    public RC4(byte[] key) {
        init(key);
    }

    private void init(byte[] key) {
        x = 0;
        y = 0;
        int keyLength = key.length;
        int i;
        for (i = 0; i < sbox.length; i++) {
            sbox[i] = (byte) i;
        }
        int j = 0;
        for (i = 0; i < 256; i++) {
            j = (j + sbox[i] + key[i % keyLength]) & 0xFF;
            Utils.swap(sbox, i, j);
        }
    }

    public byte keyItem() {
        x = (x + 1) & 0xFF;
        y = (y + sbox[x]) & 0xFF;

        Utils.swap(sbox, x, y);

        return sbox[(sbox[x] + sbox[y]) & 0xFF];
    }


    @Override
    public void setKey(byte[] key) {
        init(key);
    }

    public byte[] encrypt(byte[] data) {
        byte[] result = new byte[data.length];
        for (int i = 0; i < result.length; i++) {
            result[i] = (byte) (data[i] ^ keyItem());
        }
        return result;
    }

    public byte[] decrypt(byte[] data) {
        return encrypt(data);
    }

}
